The invention relates to a circuit for generating a sawtooth-shaped current having trace and retrace periods through a coil which, during the trace period, is connected to a trace capacitor by means of a plurality of series-arranged controllable, periodically operated switches, which switches are non-conductive substantially simultaneously during the retrace period, in which retrace period the coil, the trace capacitor and a retrace capacitance are part of a resonant network, the elements of which determine the duration of the retrace period and to which supply, energy from a supply source is applied for replenishing energy losses.
Such a circuit is disclosed in U.S. Pat. No. 3,030,444. In this prior art circuit two switches are arranged in series, that terminal of the first switch which is not connected to the second switch being coupled to a first terminal of the supply source and that terminal of the second switch which is not connected to the first switch being coupled to the second terminal of the supply source. This measure has the advantage that the pulse-shaped voltage present across the coil during the retrace period is distributed over two switches. The d.c. component of the voltage on the trace capacitor, the trace voltage, is equal to the supply voltage applied to the circuit. A given value of the trace voltage and consequently of the supply voltage is associated with a given inductance of the coil and a given amplitude of the current therethrough.